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Function expression or method is not inferable when we have mapped type with a conditional typeΒ #60047

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Description

πŸ”Ž Search Terms

conditional method arrow function

πŸ•— Version & Regression Information

  • This is the behavior in every version I tried, and I reviewed the FAQ

⏯ Playground Link

Playground Link

πŸ’» Code

type Map<T> =  { 
  readonly [P in keyof T]: T[P] extends boolean ? "boolean":  "other"
} 
export function buildCommand<F extends Record<string, unknown>>(builderArgs: { 
  func: (p: F) => void
  params: Map<NoInfer<F>>
}) {

}
type Foo = { foo: boolean };
// Function expression does not work
buildCommand({
  func: function (p: Foo) { },
  params: {
    foo: "boolean"
  }
})

// Methods don't work
buildCommand({
  func(p: Foo) { },
  params: {
    foo: "boolean"
  }
})

// Arrow function works
buildCommand({
  func: (p: Foo) => { },
  params: {
    foo: "boolean"
  }
})

πŸ™ Actual behavior

For the first two calls we get an error while the third one is successful

πŸ™‚ Expected behavior

All three calls should be successful

Additional information about the issue

Removing the constraint from F (Playground Link) or changing it to F extends Record<keyof F, unknown> (Playground Link) will remove the error.

Activity

  1. dragomirtitian commented on Sep 24, 2024

    @dragomirtitian
    ContributorAuthor
  2. Andarist commented on Sep 24, 2024

    @Andarist
    Contributor

    I happen to know a PR that fixes this: #56460

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    Domain: check: Type InferenceRelated to type inference performed during signature resolution or `infer` type resolutionPossible ImprovementThe current behavior isn't wrong, but it's possible to see that it might be better in some cases

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